What is the construction process for horizontal directional drilling rigs?

1. Measurement, Positioning, and Site Layout: Based on the design drawings and the designated pile positions, accurately mark the center line of the drilling rig, the entry point, and the exit point, ensuring these three points are aligned. Simultaneously, complete equipment placement, mud system setup, and safety fencing.

2. Drilling the Pilot Hole: Guided by the control system, the drilling rig drills along a preset trajectory to form a pilot hole. The drill bit has a built-in electronic direction finder that transmits data such as depth, inclination angle, and azimuth to a ground receiver in real time. Operators adjust the direction accordingly, ensuring trajectory deviation is controlled within allowable limits (typically lateral/longitudinal deviation ≤ 0.3 meters).

3. Staged Enlargement: After the pilot hole is completed, multiple stages of enlargement are performed using reamers of different diameters. For example, to lay a φ36-inch pipe, the hole diameter needs to be enlarged to φ48 inches or more. High-performance mud is continuously injected during the enlargement process to lubricate, protect the borehole wall, and carry away rock cuttings.

4. Pipe Retraction: The prefabricated pipe (such as PE pipe or steel pipe) is connected to the reamer via a rotary joint and slowly pulled back into the reamed borehole by the drilling rig. To protect the anti-corrosion layer, a delivery trench is used and highly lubricating mud is injected to ensure the pipe is pulled in smoothly.

5. Topographic Restoration and Inspection: After construction, the site is cleaned up, the delivery trench is backfilled, and ground-penetrating radar and other equipment are used to inspect the surface structure to confirm the absence of settlement or voids, ensuring the integrity of roads and green spaces.